Bifocal lens and method for making the same.



H A MCOURMETTES. BIFOCALLENS AND METHOD FOR MAKING THE SAME. APPLICATIONman JULY 29,1915.

Pie. 7

IN V EN TOR.

Patented Nov. 16, 1915.

of said minor disk.

nanar A. counmnrrns, or new roan, iv. Y.

:eIFocAn LENS AND METHOD FOR MAKING THEISAME.

Specification of Letters Patent.

Patented Nov. ie, 1915.

Application filed July 29, 1915. Serial N 0. 42,659.

thecounty of Kings and State of New York,

have invented an Improved Bifocal Lens and Method for Making the Same,of which the following is a full, clear, and exact description.

The objects of my invention are to correct the principal faults in thetype of welded invisible bifocal lenses, namely: 1. The fact that, owingto the deviation of the visual rays when passing through the peripheralpart of the minor disk, two objects are seen in the same place whenlooking through the line of divlsion between the upper-and lower partsof the lens; thereby causing a confused vision and a source of greadiscomgort to the wearer. In great many cases, this'fault is responsiblefor the complete inability of persons to accustom themselves to thistype of bifocals.

2. The fact that the top portion of the minor disk possesses .chromaticaberration of prism, due to the high dispersive power This causes allobjects looked at through that portion, to appear with colored edges,thereby blurring the vision.

I found that these faults could be corrected at the only condition,namely, that the line dividing the different refractive portions, shouldpass through cal center of the minor lens. I

The method consists essentiallyin filling the upper half of the recessin the major lens, with a glass similar in kind and refractive power, asthat of said major lens; thereby perfectly neutralizing the said halfand resulting in the finished lens as if no recess had been ground inthat portion ofthe major lens; and filling the, lower half of the recesswith a glass of different refractive power than that of the major lens,thereby appearing in the finished lens as a half circle minor portion,the optical center of which being on the line dividing the bifocalsurface.

The method is further illustrated in the accompanying drawing, in which,

Figure 1 is a plan view of the major lens, showing the recess in whichthe composite minor lens is to be welded. Fig. 2 is a plan view of thetwo strips of different refractive glass,

used in making the composite the exact optidisk. Fig. 3 is a similarview after welding. Fig. 4 is a plan view of the composite disk cut outfrom the welded strips. Fig. 5 is a sectional view of the compositedisk, showing the even curvature ground over the two difierent portions.Fig. 6 is a plan view of the major and minor lenses placed together andsecuredafter welding. Fig. 7 is a plan view of the welded lens, withbifocal surface finished. Fig.- 8 is aplan view of the H11- ished lens.Fig. Qis a plan view of a multifocal lens."

A major lens A having a recess or s cal curvature B ground and polishedFig. 1. A strip of low refractive glass 0 similar in kind and refractivepower as that used in the major lens A and a strip of high refractiveglass D Fig. 2 having one fiat edge each ground and polished, are weldedtogether so as to form a solid strip Fig. 3. A disk Fig. 4 cut out fromthe solid strip, and composed then of two exact half circles of glasswelded at their adjacent edges F, is ground with a spherical curvature EFig. 5, to fit the recess B of the major lens A. The composite disk isthen placed in the recess of major lens Fig. 6. with the low refractivehalf 0 toward the upper part of the major lens; the whole, thensubjected to heat until the composite disk or minor lens is thoroughlyWelded in the recess of major lens. The surface of the whole lens Fig. 7having the disk welded unto, is then ground evenly flat or curved untilthe size wanted for the reading portion is attained and the surface isthen polished. Finally the back surface of the major lens is ground andthe bifocal lens is ready to be shaped as in Fig. 8. It is understoodthat multi-focal lenses as in Fig. 9 can be made by this method.

I am aware that a patent was granted to J. L. Borsch Jr. January 21 1908#87 6,933 on welded bifocal lenses, but I am not aware that an embeddedinvisible bifocal lens having the optical center of the minor lens atthe line of junction of the different refractive portions of said lens,was ever made, therefore, i

I claim,

l. A homogeneous bifocal lens consisting of a major portion of glass anda minor portion embedded therein, the optical center of which being atthe line of junction with the pherima or portion of said lens as setforth.

glass and a minor lens embeddedv therein,

' minor portions having its optical center oo- Q a main body of beddedtherein 0 as set forth, a half circle shaped minor lens,

inciding with aboundary line of the ,major portion of said lens as setforth.

4. In an integral bifocal lens 'consisting'of glass and a minor lensemdifierent refractive powers andhaving its optical center at the centerof its straight edge as set forth. a

:5. The method of sih'a lens blank, filling and neutralizing onehalf ofthisrecess with a glass or substance similar in refractive power to thatof V the lens blank, and filling the other; half of the diiferent refracof said I I producing the bifocal l ens' 'as set forth, consisting inmaking a re- ,said recess with a glassor substance of dif- 7 so that theline of ferent refractive power, junction of the different refractiveportions passes through the optical center of the minor lens. i v- L 16. The method of producing therbifocal lens as set forth, cess in a lensblank, filling this'recess by welding into it a disk composed of onepart of glass of of lens blank and one part ofglass ofdifferentrefractive power, and surfacing the ,exposed-bifocalrsurfaceuntil the minor lens is made semi-circular. In testimony that I claimtheas my invention I name this 27th day of July 1915.

HENRY A. COURMETTES.

. In presence of- WM. 'F. YnNss, PHILIP A., Bnrrmn;

consisting in making a reforegoing, have hereunto signed my similarrefractive power to that

